1. Field of Invention
The present invention relates to surveying, in particular to a carrier for holding laths, hubs and other equipment used by surveyors in the field.
2. Description of Prior-Art
In surveying, at the beginning of a day's work, after a survey crew arrive on a job site, a foreman or party chief sets up an E.D.M. (electronic distance meter) at a control point.
A rodman, who cooperates with the party chief, loads the equipment required into a canvas bag. The equipment includes: various wooden stakes, a 2-5 Kg. (4-10 lb.) hammer, a hand-held two-way radio, 20 mm tacks, measuring tape, and a prism reflector mounted on a 152 cm (5 ft.) pointed rod.
Up to 30 of the wooden stakes, (known as "hubs" when square in cross section and "guinnes" when round), may be carried in the canvas bag. Also 30 flat wooden stakes 45 cm (18") long (known as short laths) or 122 cm (4 ft.) stakes (known as long laths) are also carried. The laths are flat wooden stakes, 38 mm (11/2") wide and 8 mm (3/8") thick and are pointed at one end for easy insertion into the ground. The top portion is spray painted in orange and has specific information, such as station name, distance, depth of cut, etc., written thereon. The short laths are then arranged in order of the surveying program to be followed that day and placed in three pockets (eight to each pocket) on the side of the canvas bag.
The party chief and rodman confer and recheck the laths and the order in which they are placed in the pockets. The party chief then points the rodman in the direction of the first station and tells him or her a specific distance to walk. The rodman then paces (steps) this distance. Then by the use of hand-held radios, the party chief tells the rodman to move to left or right, called putting the rodman "on line". Next, the rodman stands the prism reflector and its rod vertically, while the party chief takes a sample distance reading with the EDM. The party chief may inform the rodman to come closer, or move further away. More distance reading shots are taken until the rod is at the exact distance. The rodman then drives a square peg, (hub) into the ground with the hammer. A final checking shot is made with the EDM, and if the distance is correct, a concave head tack is hammered into the hub.
The position of a station, i.e., where a hub is to be hammered in, is calculated in feet and hundredths of a foot from a starting point, known as 0+00. On curved lanes the stations are closer together than on straight-line work. The rodman moves from one to the next station carrying the canvas bag of laths, the hubs, the prism rod, the hammer, the nails, the radio etc. Frequently the terrain is hilly, and the earth scarred and irregular from clearing and grading activities; this makes it difficult to find a level place to set the bag down.
Each station can take from five to twenty minutes to complete, depending on the accuracy required. I.e., surveying a street requires more accuracy than, say, the positioning of a culvert.
The problem with the canvas bag is that, being made of flexible, non-supportive material, it frequently falls or rolls over when placed on the ground. This is especially so if the location is hilly, or irregular from clearing or grading activities. The instability of the bag is also caused by the 45 cm laths being placed vertically in the pockets. Being top-heavy, they are inclined to lay down or roll over. The result is that some of the laths and other equipment often spill out onto the ground. The laths become mixed from their original specific order and before they can be replaced in the pockets, the rodman and the party chief have to confer by radio to rearrange the laths into their proper order.
Long laths, 122 cm (4 ft.) long, are too long to be placed in pockets. Sometimes these are tied together and laid along the top of the bag and tied to it by whatever method the individual can improvise. Other times a surveyor will carry a bundle of long laths under an arm. The problem here is that the bundle has to be untied to remove the needed one, then retied again in order to move along to the next station, which may be only 6 meters (20 feet) away. This is a waste of time.
It should be realized that a bundle of 4 ft. laths, a 5 ft. rod with prism reflector attached, a 10 lb. hammer, a floppy canvas bag with hubs or guinnes, and a radio constitute a very awkward load for one person to carry. It becomes even more awkward as the rodman attempts to place the canvas bag so that it will not roll or tip over.
Another problem with the canvas bag is that when four or five short laths have been taken from one pocket, there is sufficient room for the remaining three or four laths to become mixed. This can happen during carrying and without the rodman being aware of it.
The wooden hubs are 50 mm.times.50 mm.times.130 mm or 200 mm long (otherwise known as 2".times.2".times.5" or 8" hubs) and are pointed at one end. The round guinnes are 25 mm (1") in diameter and 130 mm or 200 mm (5" or 8") long, and are also pointed at one end. The sharpened points constantly wear the canvas bag during carrying, or during putting down and picking up. Thus the bag has to be frequently replaced.
In addition, 20 mm (0.75") long concave-head tacks, 15 cm (6") nails, a radio, a reflector prism and rod, a hammer, a measuring tape, and a can of spray paint are carried. Usually a 2-5 Kg (4-10 lb.) hammer is carried in the other hand.
All of the above are usually not carried at any one time. A full load may weigh up to 10 to 15 Kg. (20 to 30 lbs.)
At each location, known as a station, the rodman uses the prism rod by standing it vertically and facing it toward the party chief who is "shooting" a distance reading. There is no place on or in the canvas bag to hold the prism rod after the reading has been taken and while the hub is being hammered in.
When the hub has been driven into the ground, the prism rod point is positioned on top of the hub. The position is checked again and moved slightly, if necessary, until the exact spot is determined. Then a concave-head tack is hammered into the top of the hub in the exact spot. A 45 cm or a 122 cm lath (18" or 4') is marked with identification numbers according to the position of the adjacent hub.
The problem with the pockets being on the side of the canvas bag is that when 45 cm laths are placed vertically in them, they "take control" of the remainder of the floppy bag by pulling the bag in whatever direction the laths tend to fall due to their weight. This causes the bag seemingly to never to be sitting in the most convenient way to either remove a lath or any other object from the bag.
Surveyors also wear a belt on which some equipment is carried, such as a tape measure. Sometimes the radio is also carried on a belt since it can be damaged in the canvas bag. The problem with a belt is that the extra weight has to be carried by the person at all times, even when all the equipment carried is not needed at each station. The inconvenience of the bulk of these tools attached to the person's waist is not appreciated. Some surveyors prefer to be free of this burden by carrying all equipment in the canvas bag.
A further problem is that a handle is attached to the middle of the bag, whereas the lath pockets are along one side, such that when the bag is loaded with an equal number of hubs in the bag, and laths in the pockets, the bag is already grossly unbalanced. Also, as one hub is used, along with one lath at each station, the bag will of course remain unbalanced. To say the least, it is extremely uncomfortable and dangerous to carry, especially along uneven or hilly terrain.
If the bag were loaded only with hubs, it would be balanced. Since hubs are used one by one, the bag will remain balanced. But since common practice is to identify the inserted hub with a 45 cm lath positioned alongside, an equal number of laths must be carried. The only way to carry the laths is to stack them vertically in the three pockets provided. The tendency to imbalance is therefore great at all times.
Another problem with the canvas bag is that it lacks rigidity. Thus each time it is put down, the rodman has to make an effort to prevent it from rolling over and spilling its contents. This effort sometimes requires a number of attempts. This is frustrating and time consuming.
As said before, the bag of equipment can weigh 10 to 15 Kg. This weight must be lifted from near ground level due to the floppy nature of the bag. This creates a heavy back strain on the user.
Insofar as we are aware, no other holder for surveyor's equipment is available or known to the trade.